A method and an arrangement for detecting a changing quantity for motor vehicles are disclosed in U.S. Pat. No. 5,229,957. Here, at least one end stop of a position transducer is determined. The position transducer is coupled to an accelerator pedal of a motor vehicle which is actuated by the driver. This takes place starting from a start value during the operation of the motor vehicle in that the measured position value is continuously compared to the stored end stop value and the stored end stop value is overwritten by the actual position signal value when the position signal exceeds the stored stop value. The position signal of the accelerator pedal is evaluated for engine control and is determined on the basis of the at least one stored stop value and the measured signal value of the position transducer. A defectively detected and/or stored stop value leads to an erroneous computation of the position signal of the accelerator pedal and, in some individual cases, can lead to an unwanted control of the engine of the vehicle.
It is an object of the invention to provide measures which ensure a precise and reliable initial and/or continuous (during operation) determination of at least one stop value of a changing quantity for motor vehicles.
The solution of the invention permits a reliable and precise detection of the stop values of a measurement signal such as a position signal of an operator-actuated element of a motor vehicle.
In a preferred embodiment, it is especially advantageous that transfer resistors have no permanent influence on the stored stop value when utilizing potentiometers to detect the position of an accelerator pedal or a throttle flap. These transfer resistors can otherwise lead to lower measured values.
It is especially advantageous that the detection of the at least one stop value takes place when the position transducer is built into the motor vehicle as a new element so that a storage of a stop value based on defective data during operation of the vehicle can be effectively avoided.
This leads to the important advantage that the correctness of the learned value can be checked by the automobile manufacturer. For an exchange of components (for example, when the position transducer of the operator-controlled element or the operator-controlled element itself is exchanged), this operation must be repeated in a service station. Here too, the correctness of the value can be checked in the service center.
It is especially advantageous that the stored stop value (at the start of an operation cycle when the engine is started) is only assumed when the detected position signal satisfies special criteria. This is especially so when a change of the stored stop value is possible during operation.
It is especially advantageous that, during operation with the brake actuated and the accelerator pedal released, the determined position signal is set independently of the stored stop value to a value which represents the released accelerator pedal.
It is especially further advantageous that the stored stop value is stored in duplicate in the memory so that the duplicately stored value pair can be checked with each call up as to correctness.
Especially advantageous is the input of substitute values when there is noncoincidence of the stored stop values or for a detection operation which cannot be carried out for these stop values.